Project Summary/Abstract Cardiotoxicity is a common cause of pharmaceutical withdrawl from the market. Ideally cardiotoxicity of a drug should occur early in the development process before extensive animal testing and clinical trials are performed. The current pre-clinical cardiotoxicity testing platform relies exclusively on an in vitro test that determines whether a drug blocks a single ionic current called hERG. The FDA is calling for a change in the guidelines for in vitro pre-clinical cardiotoxicity testing. Specifically the FDA would like to include the use of human stem cell derived cardiomyocytes as part of the pre-clinical screening process. However the FDA has pointed out that the maturation state of human stem cell derived cardiomyocytes must be advanced and a high throughput electrophysiological testing platform must be developed before these cells can be used to replace the existing guidelines. CARTOX, LLC is developing cell culture plating technology that enables rapid maturation of human stem cell derived cardiomyocytes. Preliminary data shows significant maturation of the structure and function of stem cell derived cardiomyocytes using patent pending cell culture plating technology. The product that is in development is called MATURA96. MATURA96 enables rapid maturation of cells and also a platform for high throughput screening of drug effects on the human action potential. The aims of this grant are: 1. To validate the predictive power of MATURA96 for cardiotoxicity, and 2. To validate the use of MATURA96 for study of long term effects of chronic drug treatment on human cardiac physiology. Validation will be performed using FDA recommended panel of drugs with known risk (high, intermediate, low) for causing cardiotoxicity. A phase II application will be competitive if the aims of this phase I SBIR application are completed. Successful development of this product will enable the pharmaceutical and drug development industry to seriously address the 3Rs of animal usage: reduction, refinement, replacement.